وعن أبي بكرة نفيع بن الحارث الثقفى رضي الله عنه
أن النبي صلى الله عليه وسلم قال: «إذ التقى المسلمان بسيفيهما فالقاتل والمقتول في النار«قلت يارسول الله، هذا القاتل فما بال المقتول؟ قال: «إنه كان حريصاً على قتل صاحبه»
The Prophet (sallallahu alayhi wa sallam) said: “When two Muslims are engaged in a combat against each other with their sword’s and one is killed, both are doomed to Hell”. I said, “O Messenger of Allah! As to the one who kills, it is understandable, but why the slain one?” He (sallallahu alayhi wa sallam) replied: “He was eager to kill his opponent”.
Riyad as-Salihin 9, Book 1, The Book of Miscellany, Hadith 9. 1 min read